Method of transmitting and receiving high-frequency signal impulses.



F. K. VREELAND.

METHOD OF TRANSMITTING AND RECEIVING HIGH FREQUENCY SIGNAL IMPULSES. APPLICATION FILED OCT. 18. 1907. RENEWED SEPT. 18. 1911.

1 ,245, 1 66.. Patented Nov. 6, 1917.

Witnesses ventor I A M /(M ing in Montclair,county of. Essex,

STATES PATENT OFFIQE...

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flE'JEHOID OF TRANSMITTING AND RECEIVING HIGH-FREQUENCY SIGNAL IMPULSES.

. Specification of Letters Patent.

' Patented Nov. 6, 1917.

Appncation flled October is, 1907, Serial in. 397,961. Renewed September is, 1917. Serial No. 192,083.

To all whom it may concern:

Be it known that I, FREDERICK K. VREE- LAND, a citizen of the United States residtate of New Jersey, have invented a'certain new and useful Improvement in Methods of Transmitting and Receiving High-Frequency SignalImpulses, of which the following is a specification.

My invention relates to the method of transmitting and receiving sustained high frequency signal impulses involvmg the beat principle or principle of differential frequencies set forth in my application, Serial No. 350,47 6, filed January 2, 1907. By the method which constitutes the present im- .provement the signals are made imperceptis bleby any other form of receiver thus far 'produced,.the flexibility of the receiving apparatus is increased and the transmlttlng apparatus is simplified.

In carryingout my present method the transmitter is arranged tosend out a con tinuous uninterrupted train of waves and the signals consist preferably in minute variations inthe frequency of these waves, without (or with if desired) changes in intensity. These frequency changes are preferably too small to be efl'ectlvely observed by electrical resonance, although the invention is applicable where the changes are comparatively large. At the receiving end the local oscillator generates currents of a constant frequency slightly diflerentjfrom that ofthe transmitter, which produce beats in the receiver by interference with the oscillations received from the transmitter. The

nals, i. e. tones of a different pitch breaking.

in on the constant ground tone which represents the no-signal state. The ground tone 'need not necessarily be unaltera-ble. Small steady variations at either the transmitter or receiver will not affect the operativeness of the apparatus, but will only change the pitch of the ground tone on which the transitory' signal variations of tone break in.

Thus exact mutual adjustment of the twofrequencies is not required, and the receiving operator may ad ust h s own frequency be and preferablyistuned to the transmits... V.

ter frequency, to take advantage of the intensified currents due to resonance. The difference in the transmitter frequency for the slgnal and no-signal states may be so small that the receiving oscillating circuit when tuned to one frequency is practicall in tune wuth the other frequency. This iiference is preferably so small as to be beyond the range of any tuning device not embodying the principle of difi'erential frequencies. The signals are thus unobservable by any other known form of receiver. With such receivers they will seemto be a continuous wave train of unvarying frequency and intenslty.

With my resent method the oscillator of my Patent 0. 829,934 may be employed both at the transmitter and at the receiver.

This oscillator generates undamped or sustamed oscillations whose frequency depends upon the electrical constants of the system, and abrupt. changes in this frequency can be readily made by altering such electrical constants.

It is convenient to use the same oscillator alternately for sending and receiving.

As a limiting case'of this method, when the transmitter and receiver oscillations are normally (tea, in the no-signal state) exactly in tune the normal condition will be one of silence (no beats) broken by an audible beat tone when the transmitter is thrown out of tune to produce signals. Conversely, if the frequency of the receiver oscillations be exactly the same as the freuency of the transmitter signal im ulses, t e normal condition will be an audiblb beat tone broken by intervals of silence representin the signals. A similar result may be secure in a more practical wa by using a mono-telephone, a vibration ga vanometer .or relay, or other mechanically tuned receiving device, tuned to the beat frequency of the signal beats. This'will then respond only to the signal tone, the ground note producing no effect. The signals will thus stand out from a normal state of silence as when intermittent signals are employed. Or the receiver may be tuned to respond to the gmnd tone and to neglect the signal ,tone, signal then being produced by the intervals of silence. It is obvious that the beats need not be audible or even of an audible frequency, provided a receiver is employed capable of discriminating between the beat .frequencies corresponding to the signal and no-signal conditions, such as-a vibration galvanometer or relay, in which case the sl'gnalsmay be visually displayed or be recorded or both. Thus are combined the extreme selectivity arising from mechanical tunin to beats as described in my application referred to with the secrecy due to the minutely varying frequency of the continuous wave trains.

The variations of frequency at the transmitter may be readily produced by altering the electrical constants of the system in any of the ways described in my patent referred to, or in any other suitable way, such as by relatively moving two portions of the oscillator inductance thereby changing their mutual induction and hence the effective inductance of the system, or by altering the distance between theplates of a condenser thereby changing the effective capacity of the system.

'with my resent met od-to produce readily distinguis able audible toncs. Suppose the frequency of the sending oscillator be 100,000

be carried out.

" cycles per second and that of the receiving oscillator be 99,500 cycles per second, or less. Then the beat fre uency will be 100,00099,500=500 beats 2 and-a rather high pitched musical note. Ifnow the sender frequency be changed to 100,050 cycles per second higher) the beat frequency will become 550 cycles per second-a chan e of 10%, or nearly a whole tone of the musical scale, a marked interval easily observed. If the sender frequency be 100,000 and the receiver frequency be 99,900 below sender) the beat frequency will be 100 (cycles) per second (a fairly low note and a difference of only 10 oscillations, or 1 in 10,000 will produce a ..10% changein the beat frequency. A minute change in the sender frequency will therefore produce a relatively large change in the beat frequency.

In the accompanying drawing is illustrated one arrangement of apparatus by means of which the method described can --F igure 1 is a diagram representing the transmitter-and Fig. 2 is a diagram repre-j senting the receiver. The transmitting" 'o'scillator A is illustrated as a simple form of the, apparatus described in my Patent No. 829934'above referred to and consists of the vacuum tube 3 ,havingtwo anodes 4; and a cathode 5. The anodes are connected in series .in an oscillating circuit containing incycles) per sec ductances 6, 7 and capacity 8. The anodes are shunted by a circuit containing choke coils 9, 10, and between these choke coils a connection is made through the primary battery 111 to the cathode 5. The sending key 12 is shown as shunting a small portion of the inductance 6. The oscillating circuit including the oscillator is coupled with the antenna 13 by means of a transformer 14, the primary of which is formed by the inductance 7. At the receiving station the oscillator B, of thesame character as the oscillator A already described, is connected in an oscillating circuit including inductances 15, 16, and capacit 17. This oscillating. circuit is coupled ya transformerwith a tuned oscillating circuit 18 containing inductances 19,20 and also includingthe detector 21 which is illustrated as an electrostatic telephone. ,The transformer coupling the two oscillatin circuits has its primary formed by the in uctance 15, and its secondary by the inductance 19. The tuned oscillating circuit 18 is coupled with the antenna 22 by means of a transformer 23 whose primary is formed by the inductance 20. Otherarrangements of the transmitter apparatus may be "employed and any of the forms of receiver described in my application referred to may be utilized in carrying out my present method.

What I claim'is:

1. The method of transmitting and receiving sustained alternating signal impulses, which consists in transmitting a continuous Wave tram of sustained osclllatlons, changing the frequency of such continuous wave train to produce signals, combining.

with current oscillations produced by such transmitted wave train in a common element of a tuned circuit at the receiver locally generated sustainedcurrent oscillations and observing the combined efi'ects of such oscillations.

2. The method of transmitting. and receiving sustained alternating slgnal impulses, which consists in transmitting a continuous wave train of sustained oscillations, changing the frequency of such continuous wave train to produce signals, combining with current oscillations produced by such transmitted wave train ina common element of a tuned circuit at the receiverlocally generated sustained current oscillations of a different frequency and observing the beats produced by the combination of the effects of such oscillations.

3. The method of transmitting and receiving sustained alternating signal impulses, which consists in transmitting a continuous wave train of sustained oscillations, combining with current oscillations produced by such transmitted wave trainin a common element of a tuned circuit at the IGCGIVGI' locally generated sustamed current wave train to transmit signals producing at the receiver a different beat rate, and ob serving either or both beat rates.

4:- The method of transmitting and receiving sustained alternating signal impulses, which consists in transmitting a continuous wave train of sustained oscillations, combining with such transmitted wave train at the receiver locally generated sustained oscillations of different frequency producing by combination with the transmitted wave train beats corresponding with an audible tone, abruptly changing the frequency of the transmitted wave train to.

transmit signals producing at the receiver beats corresponding with a different audible tone, and observing either or both tones.

5. The method of transmitting and receiving sustained alternating signal 1mpulses, which consists in transmitting a continuous wave train of sustained oscillations, abruptly changing the frequency of said wave train to produce signals, combining I with current oscillations produced by such transmitted wave train at the receiver 10- cally generated sustained current oscillations and observing such combined oscillations by a receiver adapted to discriminate between the beat rates resulting from the different frequencies.

6. The method of transmitting and receivingsustained alternating signal impulses, which consists in transmitting a continuous wave train of sustained oscillations,

abruptly changing the frequency of said wave train to produce signals, combining with such transmitted wave train at the receiver locally generated sustained oscillations and observing such combinedoscillations by a receiver adapted to respond only to the beat rate produced by the signal frequency.

. 7. The method of transmitting and receiving sustained alternating signal impulses, which conslsts in transmitting a continuous wave train ofsustained oscillations,

producing signals by abrupt changes in the.

frequency of such wave train too small to tinuous wave train of sustained oscillations, abruptly changing the frequency of such continuous wave train to produce signals,

combining with such transmitted wave train at the receiver locally generated sustained oscillations and observing the combined effects of such oscillations.

9. The method of transmitting and receiving sustained alternating signal impulses, which consists in generating sus tained electrical oscillations, whose frequency depends upon the electrical constants of the system, producing and transmitting by such oscillations a continuous wave train, altering the electrical constants of the system to produce signals by changes in the frequency of such wave train too small to be effectively observed by electrical resonance and observing the minute variations in frequency of such transmitted wave train by comparison with a locally generated oscillation of definite frequency.

10. The method of transmitting and receiving sustained alternating signal .impulses, which consists in generating sus tained electrical oscillations, whose frequency depends upon the electrical constants of the system, producing and transmitting by such oscillations a continuous wave train, altering the electrical constants of the system to produce signals by changes in the frequency of such wave train, combining with such transmitted wave train at the receiver locally generated sustained oscillations and observing the combined effects of such oscillations.

This specification signed and witnessed this fifteenth day of October, 1907.

Witnesses:

JOHN L. LOTSGH, JAs. F. COLEMAN. 

